Field of the Invention
The present invention relates to the field of plant breeding and the development of new plants. More specifically, to the development of a new and distinct broccoli type (Brassica oleracea L. var. italica) having curds with detached florets that are uniformly green, i.e., show no yellowing or discoloration around the edges.
Background of the Invention
The botanical family to which broccoli belongs is the Brassicaceae (or referred to as Cruciferae), which is also known as the mustard family (or familiarly named as crucifers, as each flower has four distinct sepals and petals in the form of a cross). The Brassicaceae is a large family comprised of approximately 3,000 described species apportioned among 350 to 380 genera. The precise number of genera will vary depending on the authority. The classification scheme for broccoli and indeed for all of the other brassica's is clear and straightforward until one reaches the species level. At that point the addition of numerous subspecies or cultivar groups results in a rather complex and confusing arrangement of the taxa in question. For example, the scientific name for broccoli, Brassica oleracea (L.), is also shared by cabbage, Chinese cabbage, cauliflower, collards, Brussels sprouts, kale, kohlrabi, to name a few. Despite the fact that all of the aforementioned types are sexually compatible, and are therefore referred to as B. oleracea, they are nevertheless separate entities.
The genus Brassica includes a number of notable vegetable crops other than Brassica oleracea (2n=18). The Brassica genus also includes vegetables or forage crops of many other genera. Most importantly in this context are B. rapa (2n=20) or turnip and B. napus (2n=38) or swede. At the species level taxonomic names used for broccoli are Brassica oleracea L. convar botrytis (L) Alef. var. cymosa Duch, Brassica oleracea L. convar botrytis (L) Alef. var. italica Plenck and Brassica oleracea L. var italica Plenck. Taxonomic experts have different opinions for reasons mentioned before. The Germplasm Resources Information Network (GRIN), of the United States Department of Agriculture, uses Brassica oleracea L. var italica Plenck in the GRIN Taxonomy for Plants to apply to broccoli. Broccoli is hereinafter referred to as Brassica oleracea L. var italica. 
Broccoli is mostly consumed fresh. The part consumed is the fleshy-stemmed flowering head. Retailers sell such heads in its entirety. More recently, changes in fresh consumption have taken place in which the broccoli heads are separated into florets. The florets are packaged and sold as convenience foods, either solely as broccoli florets or as florets mixed with other fresh vegetables.
Many broccoli varieties grow best on well-drained soils that hold water. In sandy soils, irrigation is important for optimum plant growth and to maintain proper main curd. Curds develop relative to ambient temperatures, and in the heat of summer, broccoli curds maturing in July may produce flowers and seeds more quickly (four to six days) than those maturing in the cooler spring and fall periods.
To be considered good quality, broccoli curds should be closed, compact, dark green and tight (no yellow petals showing). A deep green, uniform curd color is a desirable trait in broccoli. Broccoli heads “green” according to the amount of sunshine reaching the crown of the curds, the crown being the upper surface of the broccoli curd covered by the florets. Current commercial ‘heading broccoli’ varieties all have a high leaf canopy that shades at least portions of the curd, particularly at the margin of the crown, resulting in yellowing around the outer extremities of the harvested broccoli curds, sometimes even causing extensive yellowing of individual florets at the center of the crown.
In a study reviewing harvest practices from 1995 to 1999 in California, broccoli production costs broken down into 29 percent for land preparation, planting, and growing costs, 45 percent for harvest and post-harvest costs, 20 percent for cash overhead, 1 percent for interest on operating capital, and 5 percent for non-cash overhead costs. Hence, the labor requirements for harvesting are well over 50% of the total labor costs for growing broccoli. Since harvesting is the single most expensive cultural operation, it is imperative that these costs be kept to a minimum. One trend is to harvest only the main terminal curd, usually by hand. Certain mechanical harvest aids are used, but complete mechanical harvesting has not been adopted. Use of modern, more uniform hybrids has enabled growers to complete harvesting in two or, at the most, three manual cuts through the field.
Converting from hand to machine harvesting of broccoli could reduce these labor requirements by a great deal. However, in testing different cultivars, transplant times, growing techniques and harvest methods, a recent study determined that once over mechanical harvest of broccoli inflorescences, or curds, compared to the graduated traditional hand-harvest (picking repeatedly 6 to 8 times), results in a yield reduction on the order of 49% to 60%, depending on the variety. A combination of hand harvest for the primary curds, followed by a mechanical picking of the secondary curds was proposed as reducing yield losses, though still on the order of about 23%.
Another issue is the cost of processing broccoli after harvesting. Broccoli curds are often further processed into individual florets, mostly by hand, for freezing or to satisfy market demand for minimally processed fresh vegetable products. The amount of hand labor is very great to cut broccoli curds into separate florets, i.e., floretting. Before floretting of the main curd, it must often be first defoliated. In addition to requiring a great deal of hand labor, the florets separated individually from the curds are generally not very uniform in size and color, and often require additional trimming and processing before packaging. In the UK, the cost of harvesting broccoli in the field is about $50 per ton. The floretting cost per ton is approximately $120 to $140 ex field. The cost for floretting in a pack house is approximately $90 per ton.
Floretting broccoli curds for use as minimally processed food is generally done at the pack house away from the growing site for hygienic reasons. For this fresh market niche, floret size is preferred in the range of 20 to 80 mm, and with a trimmed square at the cut end. Broccoli is also increasingly being grown and floretted (florets cut from the head) for frozen products. For the frozen foods market, floret size is preferred in the range of 20 to 40 mm up to 40 to 65 mm, with the 20 to 40 mm being most valuable. Freezers prefer florets that are uniform in size and green color, as more attractive to the consumer.
Green florets are preferred, though a yellow halo is inevitable, given the growth habits of current varieties. About 10% pale yellow to dark cream is tolerated on the florets. All present commercial heading broccoli varieties have curds with very tightly packed florets. This results in individual florets, once separated from the curds, having the appearance of being partially yellow in color around the edges. Additionally, all present commercial broccoli varieties have curds that are placed deeply within the canopy. As a result of the shading and lack of uniform direct sunlight, curds, as well as the stalk, do no green uniformly, but show yellow discoloration, especially around the perimeter of the curd.
Therefore, there remains a need in the art for a broccoli plant type adapted for easier processing by producing a curd with florets uniformly green in color.